How Many Sexual Partners of an Individual Need to Be Evaluated to Capture HIV/STI Risk Behavior in a Study?

Investigators conducting HIV studies ask participants multiple questions about sexual risk behaviors with their partners to ensure that they can describe the level of HIV risky sexual behavior. The assessment should be as short as possible because of the expense of collecting the data, the burden to the research subject, and ethical concerns. This study used data from the NIMH Collaborative HIV/STD Prevention Trial to answer the question about how many non-spousal/non live-in partners a research participant needs to be asked about to capture sufficient sexual risk behavior (not using a condom with a non-spousal/non live-in partner in the last 3 months). The data provided evidence that 95 % of the sexual risk behavior was captured by asking about two partners while 98 % was captured by three partners. As research funds become increasingly limited, it is important to design as parsimonious and robust a study as possible.